Air Pollution Analysis and Control: A Problem-Based Approach
Ljubisa R. Radovic
Department of Energy and Geo-Environmental Engineering, The Pennsylvania State University, University Park, PA, USA
Preface
Part I: What exactly is the problem?
Chapter 1. Air quality: introduction
1.1 Visualizing equations and statistical information
1.2 Energy demand: past, present, future
1.3 Energy supply: past, present, future
1.4 Problems
1.5 Further reading
Chapter 2. Combustion
2.1 Overview
2.2 Thermodynamics
2.3 Kinetics
2.4 Transport phenomena
2.5 Problems
2.6 Further reading
Chapter 3. Coal
3.1 Environmentally relevant properties
3.2 Combustion processes
3.3 Environmental impact
3.4 Problems
3.5 Further reading
Chapter 4. Petroleum
4.1 Environmentally relevant properties
4.2 Combustion processes
4.3 Environmental impact
4.4 Problems
4.5 Further reading
Chapter 5. Natural gas
5.1 Environmentally relevant properties
5.2 Combustion processes
5.3 Environmental impact
5.4 Problems
5.5 Further reading
Chapter 6. Other sources of air pollution
6.1 Environmentally relevant properties
6.2 Environmental impact
6.3 Problems
6.4 Further reading
Part II: What can nature do?
Chapter 7. The atmosphere
7.1 A brief introduction to micrometeorology
7.2 The atmospheric boundary layer
7.3 Velocity and temperature gradients
7.4 Problems
7.5 Further reading
Chapter 8. Pollutant dispersion
8.1 Overview of models
8.2 Box model
8.3 Simplified Gaussian plume model
8.4 EPA’s dispersion models
8.5 Acid rain and smog
8.6 Problems
8.7 Further reading
Part III: What must society do?
Chapter 9. The essential aspects of air quality legislation
9.1 Clean Air Act and amendments
9.2 Kyoto Protocol and its future
9.3 Problems
9.4 Further reading
Chapter 10. Particulate matter
10.1 Overview of control strategies
10.2 Filtration
10.3 Electrostatic precipitators
10.4 Problems
10.5 Further reading
Chapter 11. Sulfur oxides
11.1 Overview of control strategies
11.2 Absorption
11.3 Fluidized-bed combustion
11.4 Problems
11.5 Further reading
Chapter 12. Carbon oxides
12.1 Overview of control strategies
12.2 Absorption
12.3 Catalytic converter
12.4 Problems
12.5 Further reading
Chapter 13. Nitrogen oxides
13.1 Overview of control strategies
13.2 Adjustment of temperature and combustion stoichiometry
13.3 Adsorption
13.4 Selective catalytic reduction
13.5 Problems
13.6 Further reading
Chapter 14. Volatile organic compounds
14.1 Overview of control strategies
14.2 Adsorption
14.3 Incinerators
14.4 Problems
14.5 Further reading
Chapter 15. Air quality: summary
15.1 Will ‘natural capitalism” work?
15.2 “Cradle-to-cradle” opportunities for energy and materials
15.3 Problems
15.4 Further reading
Appendix
Answers to selected problems
CD (and web site)
Index
Preface
This (text)book seeks to implement a powerful learning strategy in a field that is of interest to readers with increasingly diverse backgrounds. Air quality is of interest to at least chemical, environmental and mechanical engineers. Furthermore, engineers (or engineers-to-be) are increasingly recognizing that solutions to environmental problems require familiarity with socio-political issues. And both professional and part-time politicians increasingly feel that the weight and impact of their environment-related decisions requires some familiarity with the underlying science and technology. I have confronted the special challenges that these dichotomies present by offering the reader not only a “hands-on” approach to each one of the relevant topics, but also a broad coverage of all their essential aspects. In today’s information-saturated world -- where almost all the information (both reliable and not-so-reliable) is available online at any time and increasingly at any place -- the purpose of a textbook must be to clearly identify, and thus include within its covers, only the essential aspects of all the key issues. The relevant details, including some of the important ones, should be left for the interested reader to easily find using the amazing powers of the googles of this world. I have sought this simultaneous breadth and depth of coverage by introducing all the basic scientific, technological and socio-political issues and quickly culminating their discussion with a large number of worked-out examples. And what is even more important for the success of such learning strategy, the parametric sensitivity of all the equations that describe the key phenomena is further explored in the end-of-chapter problems; there is nothing more important for true understanding than being able to quickly provide and visualize the answers to such “what if” questions.
It is in this sense, and not so much in the selection of topics, that this monograph diverges from what is currently available in the bibliography of air quality assessment and control. The extent of coverage of each topic was carefully pondered to satisfy the often conflicting demands of both a design engineer and an informed (and concerned!) citizen. The scientifically and technologically inclined readers will hopefully find all the quantitative aspects of each topic (admittedly not in sufficient depth to meet all their needs): the impact of stoichiometry, thermodynamics, kinetics and transport phenomena on the formation, dispersion and control of air pollutants. For the readers more interested in the qualitative aspects of each topic, the applicable equations can be taken for granted and their meaning is then revealed by the many graphs constructed from them; special emphasis is given to graphs that can become a good basis for environmental policy decisions.
Part I is devoted to defining the nature of the air pollution problem in precise quantitative terms: how many kilograms of a pollutant of interest will be emitted into the atmosphere over a certain period of time? This is important because many environmental and air quality issues are too often diluted into descriptive arguments which neither culminate in clear definitions of technological options nor convey a sense of urgency for some of the looming environmental policy decisions. Thus, for example, only when the projected growth of world’s electricity demand is confronted with the currently available renewable energy options does it become abundantly clear how large a role the fossil fuels will continue to have in the 21st century, and this in turn highlights how much more ubiquitous and more efficient the air pollution control devices must become in order to avoid the melting of polar ice and preserve and improve the quality of the air that we breathe. Therefore, a discussion of both the virtues and the liabilities of fossil fuels and their combustion, which accounts for the vast majority of air pollution, is presented in quantitative terms. Special emphasis is placed on identifying the straightforward links between scientific issues and policy options. A typical example is the impact of the elemental composition of U.S. coals: when an electric power plant switches from high-sulfur bituminous coal to low-sulfur subbituminous coal, in order to reduce its SO2 emissions and solve the acid rain problem, there is an increase in its CO2 emissions, and this has the potential of resulting in a more serious global warming problem.
Having concluded in Part I that fossil fuel combustion and its potential air pollution will be with us for much of the 21st century, in Part II we explore to what extent the solution to pollution is dilution. The specific question to be answered here is how to convert, for example, the kilograms per second of pollutant emission (discussed in Part I) into kilograms per cubic meter of pollutant concentration, which is what determines the danger to air quality. Because the behavior of earth’s atmosphere is a complex interplay of phenomena governed by thermodynamics, fluid dynamics and heat and mass transport, the use of models is presented as a convenient and inevitable tool for predicting how far the air pollutants will spread (or ‘disperse’) once they are emitted from a pollution-producing device (a so-called “point source”). While the important details of model construction are beyond the scope of our discussion, great effort is expended to avoid the GIGO syndrome (“garbage in = garbage out”) by taking a close look at some of the key parameters in models of varying degree of complexity and showing their impact on the predictions of pollutant concentrations.
Having concluded in Part II that building a taller smokestack or relying on favorable wind is often not the solution to air pollution, Part III provides a summary of the most important strategies currently available to reduce pollutant emissions. The emphasis is again on showing how thermodynamics, kinetics and transport phenomena govern the phenomena of interest, in this case to increase the efficiency of pollution control devices.
This book is an outgrowth of several courses that I have been teaching over the past decade, mostly in the Energy and Geo-Environmental Engineering Department at Penn State but also at the University of Queensland and University of Concepción. My warmest thanks go to the colleagues in the Chemical Engineering Department of both these institutions for the friendly and stimulating atmosphere that made the course development possible.
Ljubisa R. Radovic
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University Park, PA, July 2007
1.1 Visualizing equations and statistical information
The great advantage of today’s easy access to mathematics software (e.g., Mathematica, Matlab; and Excel, of course) is the opportunity to translate quickly even the more complicated multi-parameter equations into graphs that can be readily understood. This learning strategy will be implemented throughout the book, so here it is important to introduce it and illustrate its power.
Broadly speaking, the information of greatest relevance to air pollution problems falls into one of two categories: (a) equations that summarize the chemistry and/or physics of the underlying phenomena, and (b) statistical data describing historical trends or future projections for energy consumption and air pollutant accumulation. Example 1-1 is an illustration of the former and Example 1-2 of the latter. In each case, for now, the content of the Excel workbook and the Mathematica notebook can be viewed as a “black box”; as we make progress, many such algorithms will be analyzed in considerable detail and their preparation should thus become second nature in our pursuit of mastery of any topic.
Example 1-1. The Zeldovich1.nb Mathematica file can be used to determine the temperature dependence of nitrogen oxides emissions. By using the Zeldovich mechanism (see Chapter 13) it is shown that 520 ppm of NO are expected to be emitted at 2250 K, 10 atm and 0.005 s. Construct a graph that shows the concentration of NO produced as a function of temperature (e.g., from 1800 to 2700 K) and pressure (e.g., from 0.1 to 100 atm).
Example 1-2. Download the relevant data file(s) from the web site of the U.S. DOE’s Energy Information Agency (www.eia.doe.gov) and construct a graph that clearly shows whether there has been a shift in the use of energy sources by the electric power plants. Based on your reading of recent media reports, what kind of shift do you expect to see, if any?
1.2 Energy demand: past, present and future
1.3 Energy supply: past, present and future
1.4 Problems
1.5 Further reading